Search Results

Usually the power output of 50 cm₃ two wheelers is higher than necessary to reach the maximum permitted vehicle speed, making engine power restriction necessary. This publication deals with different power restriction strategies for four-stroke engines and their effect on exhaust emissions. Alternative power limitation strategies like EGR and leaning were investigated and compared with the common method of spark advance reduction to show the optimization potential for this certain engine operation conditions. From these tests, a substantial set of data showing the pros and cons in terms of emissions, combustion stability and fuel economy could be derived for each speed limiting technique.

Affordable, efficient and durable catalytic converters for the two and three wheeler industry in developing countries like India are required to reduce vehicle emissions and to maintain them at a low level and therefore to participate in a cleaner and healthier environment. A new generation of metallic substrates with structured foils for catalytic converters has been proven capable of improving conversion behavior even with smaller catalyst size. Specially developed foil structures which transform a laminar exhaust gas flow into a turbulent one, which significantly improve exhaust gas mixing behavior in the catalyst. This publication will deal with the analysis of different metallic substrate foil structures for the catalyst conversion performance for the leading “state of the art” four stroke 150 cm3 motorcycle technology developed for the Asian market.

This publication covers investigations on different 3D CFD models for the description of the spray wall and droplet-fluid interaction and the influence of these models on the mixture formation calculation results. Basic experimental investigations in a spray chamber and a flow tunnel as well as the corresponding 3D CFD simulation were conducted in order to clarify the prediction quality of the physical phenomena of spray-wall and spray-fluid interaction by the simulation. Influencing parameters such as the piston top temperature, piston bowl geometry, soot deposits on the piston top as well as flow velocity are investigated. This paper provides a direct link between the underlying simulation models of the mixture formation and actual real world combustion system development processes - underlining the importance of a close interaction of the model calibration and the development process.

In the course of the last few years a continuous increase of the injection pressure level of gasoline direct injection systems appeared. Today's systems use an injection pressure up to 200bar and the trend shows a further increase for the future. Although several benefits go along with the increased injection pressure, the disadvantages such as higher system costs and higher energy demand lead to the question of the lowest acceptable injection pressure level for low cost GDI combustion systems. Lowering injection pressure and costs could enable the technological upgrading from MPFI to GDI in smaller engine segments, which would lead to a reduction of CO2 emission. This publication covers the investigation of a low pressure GDI system (LPDI) with focus on small and low cost GDI engines. The influence of the injection pressure on the fuel consumption and emission behavior was investigated using a 1.4l series production engine.

The development process of 2-stroke engines is characterized by limited CFD investigations in combination with long-term development phases on the test bench with high prototype costs. To reduce the costs and to realize shorter development time together with a higher prediction quality of the engine potential, a higher implementation level of 1D and 3D simulation tools into the development process is necessary. This publication outlines the 1D simulation methods in the layout phase of GDI combustion processes of 2-stroke engine categories. By means of conceptual investigations, the demands, the potential and the limits of 1D CFD simulation methodology are defined. Using a comparison between 1D and 3D or 1D/3D coupled simulation methods the limits of solely 1D simulation are shown. For advanced simulation tasks with a higher demand for prediction quality, the entire engine is simulated in 1D, whereas special parts of the engine design are simulated in a 3D model.

Thanks to its unsurpassed power-to-weight ratio, its low package space and low-maintenance design, the loop-scavenged two-stroke engine with conventional mixture preparation is still being used in some sectors of vehicle engineering, such as boat drives, snow mobiles and motor scooters, as well as in hand-held applications. To maintain the potential of the 2-stroke engine for the future it is necessary to take adequate steps against the system-dependent disadvantage of the simple 2-stroke engine, namely that of higher emissions compared to 4-stroke engines. One possible solution is gasoline direct injection. Its more frequent use will increase the production numbers, making it an interesting technology even in the above-mentioned cost-sensitive applications. The current report presents various concepts of direct injection in 2-stroke engines, from air-assisted injection through to high-pressure direct injection, and compares them with traditional techniques of mixture formation.

Future emission regulations for two wheeler vehicles driven by small capacity engines will include the cold start characteristics and the durability behavior. [1] Based on the European homologation cycle ECE R47 and an additional cold start test cycle, a number of scooters driven by 50cc engine concepts in combination with different exhaust gas after treatment strategies have been analyzed and evaluated. The test series have been performed with the help of a CVS measurement system according the European homologation instruction and in addition with the help of an online emission recorder measurement.

On the basis of small hybrid powertrain investigations in hand-held power tools for fuel consumption and emissions reduction, the prototype hybrid configuration of a small single-cylinder four-stroke internal combustion engine together with a brushless DC electric motor is built and measured on the testbench in terms of efficiency and emissions but also torque and power capabilities. The onboard energy storage system allows the combustion engine electrification for controlling the fuel amount and the combustion behavior while the electric motor placement instead of the pull-start and flywheel allows for start-stop of the system and load point shifting strategy for lower fuel consumption. The transient start-up results as well as the steady-state characterization maps of the system can set the limits on the fuel consumption reduction for such a hybrid tool compared with the baseline combustion-driven tool for given load cycle characteristics.

As the number of different engine and vehicle concepts for powered-two wheelers is very high and will even rise with hybridization, the simulation of emissions and fuel consumption is indispensable for further development towards more environmentally friendly mobility. In this work, an adaptive artificial neural network based predictive model for emission and fuel consumption simulation of motorcycles operated in real world conditions is presented. The model is developed in Matlab and Simulink and is integrated into a longitudinal vehicle dynamic simulation whereby it is possible to simulate various and not yet measured test cycles. Subsequently, it is possible to predict real drive emissions RDE and on-road fuel consumption by a minimum of previous measurement effort.

The automotive industry has made great efforts in reducing fuel consumption. The efficiency of modern spark ignition (SI) engines has been increased by improving the combustion process and reducing engine losses such as friction, gas exchange and wall heat losses. Nevertheless, further efficiency improvement is indispensable for the reduction of CO2 emissions and the smart usage of available energy. In the previous years the Atkinson Cycle, realized over the crank train and/or valve train, is attracting considerable interest of several OEMs due to the high theoretical efficiency potential. In this publication a crank train-based Atkinson cycle engine is investigated. The researched engine, a 4-stroke 2 cylinder V-engine, basically consists of a special crank train linkage system and a novel Mono-Shaft valve train concept.

The Institute for Internal Combustion Engines and Thermodynamics, Graz University of Technology, has presented several applications of its 2-stroke LPDI (low pressure direct injection) technology in the previous years ([1], [2], [3]). In order to improve the competitiveness of the 2-stroke LPDI technology, an air cooled 50cm3 scooter application has been developed. All previous applications have been liquid cooled. This air cooled application demonstrates the EURO 4 (2017) ability of the technology and shows that the 2S-LPDI technology can also be applied to low cost air-cooled engines. Hence, the complete scooter and moped fleet can be equipped with this technology in order to fulfil both the emission standards and the COP (conformity of production) requirements of Euro 4 emission stage. The paper presents the Euro 4 Scooter results and describes the efficient conversion process of the existing carburetor engine to the LPDI version.

In industrial processes and other power generation processes, large amounts of waste heat are often lost to the environment. The conversion of this thermal energy into mechanical work promises a significant improvement in energy-utilization, the efficiency of the overall system and, consequently, cost-effectiveness. Therefore, the use of a Rankine-Cycle is a well-established technical process. A recent research project has investigated a novel expansion machine to be integrated into such an RC-process. Primarily, the present work deals with the fluid dynamic simulation of this expander, which is based on the principle of a rotary piston engine. The aim is to develop, analyze and optimize the process and the corresponding components. Hence, a CFD-model had to be built up, which should correspond as closely as possible to the physical engine.

Based on the fundamental analysis of the two-stroke process and the first results of the 3D-CFD simulation (Paper No: SETC 2005-32-0098), the development of a small capacity two-stroke engine is the subject of this publication. The developed 50 cm3 two-stroke engine is applied with a low pressure fuel injection system and allows, due to the special positioning of the fuel injector, two different scavenge modes. The first mode is a standard homogenous scavenge mode and the second one is for a stratified scavenged engine operation. Both modes can be achieved only by the adjustment of the injection timing without any restrictions concerning possible phasing. The system only deals with one fuel injector; special constraints concerning the transition between stratified and homogenous operation are not required. Any possible mixture can be applied between stratification and homogenous mode.

This publication presents the development of a GDI combustion system for high speed - high performance engines. The paper describes the development of the combustion process and its results, the development methodology, covering 1D and 3D CFD simulations, and shows extensive experimental investigations. With 3D CFD simulations the necessary deeper insights in the mixture preparation process of a homogenous GDI combustion system are gained. The findings of the simulation are transferred to an injection and combustion system for a 4-cylinder test engine. The results of the experimental investigations of the 4-cylinder engine equipped with GDI technology show the potential of GDI applications for high performance engines.

In the early phase of an engine development process, the main characteristics of an engine setup, such as lengths, diameter and volumes, are usually defined by means of 1D CFD simulation technologies. Only single flow situations are modeled in 3D due to the high expenditure of time and money. This paper presents a new efficient development methodology using 1D, 3D as well as coupled 1D/3D simulation techniques - the described simulation strategy leads to a more realistic and more comparable reproduction of the flow situation, especially in the critical areas of the simulation domain, while avoiding the restrictions and disadvantages of 1D and 3D simulation. By the use of test bench results of a comparable prototype engine, the quality of the simulation strategy has been successfully verified.

Looking at the market for 2-wheelers driven by small capacity four stroke engines, it turns out that the legislation for exhaust emissions is mostly combined with a regulation of vehicle speed. Most of the vehicles in this category are still driven by engines equipped with carburetors which, unlike fuel injection systems, do not give the possibility to cut off fuel metering when high speed is achieved. When a carburetor is applied with a simple ignition unit, a reduction of spark advance is the only way to ensure correct vehicle speed, but there are a lot of disadvantages in terms of exhaust emissions and fuel economy coming up with this method of engine power restriction. This leads to the idea of using exhaust gas recirculation (EGR) to reduce engine power when necessary.

For the development of high-performance 2-stroke engines with internal mixture preparation it is essential to know about the interaction between charge motion and injection spray. With no prototypes available conceptual investigations can only render such information by using 3D CFD simulation. In this way an optimization of mixture preparation and charge motion can be achieved by varying the transfer and boost ports. To allow for the influence of these modifications on the mass balance (volumetric and trapping efficiency), the entire system of the loop-scavenged two-stroke engine has to be investigated. The state of the art calculation domain for 2-stroke 3D CFD simulation is bounded at the inlet of the crankcase (reed valve) and sometimes also at the outlet of the cylinders. The reasons lie in the so far not sufficiently reproducible components (e.g. reed valve) as well as in the reduction of calculation time.

The new generation of metallic substrates for catalytic converters used in the two and three wheeler industry is capable of improving conversion behavior even with smaller catalyst size. The lowering of production costs due to less use of precious metal is possible. This novel technological application in motorcycle vehicle class improves exhaust emission performance and introduces a new competitive product on the market. Specially developed foil structures, which transform a laminar exhaust gas flow to a turbulent one, significantly improve exhaust gas mixing behavior in the catalyst. This publication is dealing with the analysis of different metallic substrate foil structures for the catalyst conversion performance and the light-off characteristics for the leading state of the art four stroke 150 cm3 motorcycle technology developed for the Asian market.

Meeting future legislative targets for SI engines by means of low cost technologies is a big challenge for engineers. Despite the use of simple and cost efficient components these engines have to fulfill customer requirements in terms of power and fuel economy, representing the most important selling arguments. Without the possibility of integrating modern technologies like fuel injection systems for mixture preparation instead of simple carburetors, it is very complex to find viable solutions that enable the achievement of these targets. A main key to improve emission behavior, fuel economy and performance on carbureted engines is to get an insight in the mixture preparation process, especially under transient conditions.

Nowadays, politicians are forced by air pollution prevention to demand zero emission vehicles (ZEV) in the form of pure electric vehicles. The poor capacity to weight factor of actual batteries compared to any kind of liquid or gaseous hydro-carbon fuel is the main reason for the retarded implementation of ZEV. Solutions offered by automobile manufacturers are mild to full hybrid powertrains based on the well established ICE platform. The difficulty of those approaches of electrification is to compete with the performance and benefit costumers expect from standard automobiles. Pure electric vehicles are rare and often disappointing regarding range and/or performance. Additionally the costs for such vehicles, which are mainly driven by the battery prices, are comparatively high, impeding their market entrance and acceptance. Low price electric city scooters are actually offered as pure electric vehicles in a wide variety of different models.